1. Field of the Invention
This invention relates to a catalyst for the production of an oxygen-containing compound and to a method for the production of an oxygen-containing compound. More particularly, It relates to a catalyst intended for producing an oxygen-containing compound by oxidizing an olefin, an alcohol, or an aldehyde with a polyoxo metalate substituted with a transition metal and serving as a catalyst in the presence of a molecular oxygen-containing gas and to a method for producing the oxygen-containing organic compound. still more specifically, it relates to a catalyst for producing an epoxide compound by oxidizing an olefin, a carbonyl compound by oxidizing an alcohol, or a carboxylic acid by oxidizing an aldehyde and to a method for producing the catalyst.
2. Description of the Related Art
The reaction of oxidation is one of the important and basic reactions in the industry of organic chemistry. Generally, the method of nitric acid oxidation using nitric acid as an oxidizing agent is most widely known. Since this method entails emission of N.sub.2 O and NO.sub.x, however, it necessitates the attachment to the reaction vessel of an extra device intended to remove such nitrogen oxides. As other oxidizing agents, chromic acid and manganese compounds are well known. Since the method of interest uses such a metal compound in a large amount, it also necessitates an aftertreatment such as recovery. Now that particularly the problems of natural resources and environment are attracting attention, the conventional method reveals itself to have room for further improvements When the reaction of oxidation is enabled to be directly effected by using molecular oxygen or air as an oxidizing agent in the presence of a catalyst, therefore, a fair method of production can be afforded. Since the activation of oxygen generally requires a high temperature and a high pressure, no high selectivity can be hoped for in the production aimed at. Thus, for the purpose of alleviating the reaction conditions, it has been proposed to use an alcohol or an aldehyde as a co-oxidizing agent or a reducing agent. This proposed use is still problematic because it entails by-production of a relevant aldehyde or organic acid.
JP-A-08-38,909 and JP-A-2000-212,116 disclose a method for producing a ketone, an aldehyde, an organic carboxylic acid, etc. by the oxidation with oxygen under comparatively mild reaction conditions, with a specific imide compound such as N-hydroxyphthal imide used as a main catalyst. This method, however, cannot be rated as excellent because the imide compound catalyst discharging the role of a radical generating agent is decomposed or wasted during the course of the reaction and because the amount of the catalyst to be used is large relative to the substrate for reaction is unduly large. A method which, in the production of glycolic acid by the oxidation of ethylene glycol with an oxygen-containing gas, uses a catalyst incorporating a lead compound in platinum and/or platinum is disclosed in JP-A-54-132,519. This method, however, ought to supply the reaction system with an alkali and naturally suffers the carboxylic acid to transform into an alkali salt and, therefore, needs to give the reaction system a treatment for neutralization and desalination.
To cite the reaction for epoxidizing an olefin, for example, the fact of synthesizing an epoxide by adding one oxygen atom to a carbon-carbon double bond constitutes itself one of the important methods of chemical conversion. The epoxide is often utilized as an intermediate compound which can be converted into an end product. The reaction for epoxidizing an olefin can be implemented by numerous techniques. The oldest and most general method for this reaction consists in having an olefin react with an organic peracid (as taught, for example, in JP-A-04-169,576). Typical peracids are perbenzoic acid, peracetic acid, and the like. The salts of such acids also serve as effective oxidizing agents. This method of reaction, however, entails several defects. The first of the defects resides in the fact that the reaction of epoxide with water and/or the acid in the reaction solvent is liable to form such by-products as a glycol and a glycol ester. The second thereof resides in the fact that the by-produced acid must be recovered or recycled And the third thereof resides in the fact that since the reaction uses an organic peracid, it must be controlled strictly from the viewpoint of ensuring safety.
Methods for effecting an expected oxidation with hydrogen peroxide or an organic hydroperoxide by using a compound containing Ti (IV), V (V), Mo (VI), or W (VI) or titanosilicate as a catalyst with a view to lessening the danger caused with a peracid have been proposed (the official gazettes of JP-B-40-26,184 and BP 100,119). The hydroperoxides which are generally used for such reactions are tertiary butyl peroxide, cumene peroxide, ethyl benzene peroxide, and the like. These reactions are safe because the reactants used therein have low reactivity as compared with the organic peracids. They nevertheless are liable to induce (such secondary reactions as) a reaction of displacement at the allylic position of an olefin and a reaction of oxidation in the place of the addition of oxygen to the double bond.
Where a compound containing Ti (IV), V (V), Mo (VI), or W (VI) or titanosilicate in used as a catalyst and the aqueous solution of hydrogen peroxide is used as an oxidizing agent, the process forms water as a by-product and, therefore, brings a tender effect on the environment and obviates the necessity for recovery or recyclization. When hydrogen peroxide is used additionally, titanium silicate (TS-1), titanium-substituted zeolite (disclosed, for example, in EP 100,119, WO 9747614, and 4,833,260), and various heteropoly acids (disclosed, for example, in JP-A-62-234,550) are used as effective and selective catalysts.
In many cases, the aqueous solution of hydrogen peroxide is used as an ideal oxidizing agent where the reaction is selective. Unfortunately, however, the formed epoxide is caused by water to encounter ring opening and suffer from a decline in yield. There are times when the hydrogen peroxide becomes relatively expensive when the price of the epoxide is low.
Incidentally, the ideal oxidizing agent for the epoxidization of an olefin is ecologically and economically the molecular oxygen (dioxidine) which exists in the air. The addition of dioxidine to an olefin is thermodynamically unfavorable and requires a catalyst. The basic problem that confronts the use of dioxidine for the epoxidization of an olefin consists in the fact that the molecular oxygen is possessed of a radical quality. In a homogeneous reaction, this radical quality infallibly induces a radical reaction preferentially through the route of the displacement of the hydrogen atom attached to the carbon atom at the allylic position. The use of a dioxidine in a catalytic reaction performed in a liquid phase, therefore, encounters difficulty in obtaining an epoxide as a main product.
Recently, as a major trend of the development of such reactions of oxidation, numerous catalyst systems which, by activating oxygen in the presence of a reducing agent and effecting a reaction of the in vivo mono-atomic oxygen adding enzyme type under comparatively mild conditions, are enabled to manifest high selectivity despite low activity have been proposed. Conceptually, the use of molecular oxygen in the reaction of epoxidization of an olefin ought to necessitate the formation of a metal oxo compound of high valency which occurs after the cleavage of an oxygen-oxygen bond. The metal oxo intermediate or such high valency serves as an effective epoxidizing agent. For the purpose of effecting the reaction of expxidization of an olefin by the cleavage of an oxygen-oxygen bond, however, the formation of an active metal oxo intermediate of high valency generally requires extraction of two electrons from the reducing agent. An example of obtaining in a high yield an epoxide by the reaction of epoxidization of an olefin by using an alcohol or an aldehyde as an electron donor is reported (Bull. Chem. Soc. Jpn., 1991, 64, 2513). This reaction is not favorable because it forms an aldehyde or an acid at the same time. An example of using hydrogen as a reducing agent has also been reported. JP-A-04-352,771 discloses a method for producing propylene oxide by the reaction of propylene with hydrogen and oxygen in the presence of a catalyst formed of a metal of Group VIII in the Periodic Table of the Elements and a crystalline titanosilicate. Japanese Patent No. 2,615,432 discloses a method for producing an epoxide by the oxidation with oxygen of an unsaturated hydrocarbon in the presence of molecular oxygen, hydrogen, and a catalyst containing gold and titanium dioxide. These methods invariably are problematic because they produce an epoxide in low yield and require to use dangerous and expensive hydrogen.
Besides, the mechanism of the dioxinase type is capable of activating molecular oxygen without requiring the presence of active hydrogen. In this reaction, the molecular oxygen is cleaved by using two metal cores and enabled to form two metal oxo species of high valency. An example of using a Ru-substituted tetramesytyl porphyrin [J. Am. Chem. Soc., 107, 5790 (1985)] may be cited. This catalyst, however, manifests unusually low activity to the epoxide and exhibits no perfect stability thermally in an atmosphere of oxygen.
JP-A-05-213,917 discloses a method for producing an epoxide compound by oxidizing an olefin compound with molecular oxygen in the presence of a catalyst formed of the onium salt of a heteropoly acid having tungsten as a poly atom or a derivative thereof without requiring use of such a reducing agent as hydrogen, i.e. an electron doner. This reaction produces an epoxide still in low yield.
An example of epoxidizing an olefin by using molecular oxygen as an oxidizing agent in the presence of a transition metal-substituted polyoxo metalate serving as a catalyst has been known. WO98/54165 discloses transition metal polyoxo metalate [WznRu.sub.2 (ZnW.sub.9 O.sub.19).sub.2 ].sub.11 as a catalyst. The same inventor reports the same catalyst system in Nature, Vol. 388, Jul. 24 1997, pages 353-355. The report clearly describes that the hydroxylation of an alkane catalytically proceeds and that the hydroxylation of adamantane, for example, has 100 as the number of turnovers and the epoxidization of an alkene does not proceed catalytically under standard conditions.
An object of this invention, therefore, is to provide a novel catalyst for the production of an oxygen-containing organic compound and a novel method for the production of the oxygen-containing organic compound.
Another object of this invention is to provide a method for producing an oxygen-containing organic compound safely and economically in satisfactorily high yield from an olefin, an alcohol, or an aldehyde by using molecular oxygen as an oxidizing agent for the production of intetest.
Still another object of this invention is to provide a novel catalyst for producing an epoxide compound by the oxidation of an olefin, a carbonyl compound by the oxidation of an alcohol, or a carboxylic acid by the oxidation of an aldehyde and a novel method for the production of such a compound.